mandelbrot.c

/*
c program:
--------------------------------
 1. draws Mandelbrot set for Fc(z)=z*z +c
 using Mandelbrot algorithm ( boolean escape time )
-------------------------------
2. technique of creating ppm file is  based on the code of Claudio Rocchini
http://en.wikipedia.org/wiki/Image:Color_complex_plot.jpg
create 24 bit color graphic file ,  portable pixmap file = PPM
see http://en.wikipedia.org/wiki/Portable_pixmap
to see the file use external application ( graphic viewer)
 */
#include <stdio.h>
#include <math.h>
int main()
{
         /* screen ( integer) coordinate */
       int iX,iY;
       const int iXmax = 4000;
       const int iYmax = 4000;
       /* world ( double) coordinate = parameter plane*/
       double Cx,Cy;
       const double CxMin=-2.5;
       const double CxMax=1.5;
       const double CyMin=-2.0;
       const double CyMax=2.0;
       /* */
       double PixelWidth=(CxMax-CxMin)/iXmax;
       double PixelHeight=(CyMax-CyMin)/iYmax;
       /* color component ( R or G or B) is coded from 0 to 255 */
       /* it is 24 bit color RGB file */
       const int MaxColorComponentValue=255;
       FILE * fp;
       char *filename="mandelbrot.ppm";
       char *comment="# ";/* comment should start with # */
       static unsigned char color[3];
       /* Z=Zx+Zy*i  ;   Z0 = 0 */
       double Zx, Zy;
       double Zx2, Zy2; /* Zx2=Zx*Zx;  Zy2=Zy*Zy  */
       /*  */
       int Iteration;
       const int IterationMax=200;
       /* bail-out value , radius of circle ;  */
       const double EscapeRadius=2;
       double ER2=EscapeRadius*EscapeRadius;
       /*create new file,give it a name and open it in binary mode  */
       fp= fopen(filename,"wb"); /* b -  binary mode */
       /*write ASCII header to the file*/
       fprintf(fp,"P6\n %s\n %d\n %d\n %d\n",comment,iXmax,iYmax,MaxColorComponentValue);
       /* compute and write image data bytes to the file*/
       for(iY=0;iY<iYmax;iY++)
       {
            Cy=CyMin + iY*PixelHeight;
            if (fabs(Cy)< PixelHeight/2) Cy=0.0; /* Main antenna */
            for(iX=0;iX<iXmax;iX++)
            {
                       Cx=CxMin + iX*PixelWidth;
                       /* initial value of orbit = critical point Z= 0 */
                       Zx=0.0;
                       Zy=0.0;
                       Zx2=Zx*Zx;
                       Zy2=Zy*Zy;
                       /* */
                       for (Iteration=0;Iteration<IterationMax && ((Zx2+Zy2)<ER2);Iteration++)
                       {
                           Zy=2*Zx*Zy + Cy;
                           Zx=Zx2-Zy2 +Cx;
                           Zx2=Zx*Zx;
                           Zy2=Zy*Zy;
                       };
                       /* compute  pixel color (24 bit = 3 bytes) */
                       if (Iteration==IterationMax)
                       { /*  interior of Mandelbrot set = black */
                          color[0]=54;
                          color[1]=145;
                          color[2]=230;
                       }
                    else
                       { /* exterior of Mandelbrot set = white */
                            color[0]=255; /* Red*/
                            color[1]=255;  /* Green */
                            color[2]=255;/* Blue */
                       };
                       /*write color to the file*/
                       fwrite(color,1,3,fp);
                       // printf("CXMin-value = %f, Cx = %f\n CYMin-Value= %f, CYValue= %f\n", CxMin , Cx, CyMin, Cy);
               }
       }
       fclose(fp);
       return 0;
}